Acoustic pianos such as conventional grand pianos and upright pianos are configured of many components. Assembling these components is very complex, and thus assembling work takes long time. In particular, an action mechanism provided so as to correspond to each key requires many components, and thus its assembling work and adjustment is very complex.
For example, in the action mechanism described in Japanese Patent Application Laid-Open No. 2005-292361, a plurality of components mutual act to cause a key operation by key depressing and key releasing to be transmitted to a hammer. In particular, a support assembly configuring a part of the action mechanism operates with various components combined together. The support assembly has not only a mechanism achieving string hitting by the hammer in accordance with key depressing but also an escapement mechanism for releasing a force transmitted to the hammer by key operation immediately before key hitting. This mechanism is an important mechanism for achieving basic operation of an acoustic piano. In particular, in a grand piano, double escapement mechanism with a repetition lever and a jack combined together is generally adopted.
The operation of the action mechanism gives a sense (hereinafter also referred to as “touch feeling”) to a finger of a player through a key. In particular, the configuration of the support assembly has an important influence on the touch feeling. For example, the touch feeling by operation of the escapement mechanism is called let-off.